* Steak should be 3/4 inch thick. ** Onion should be thickly sliced. Cut steak into 4 pieces; rub with salt and pepper. Heat butter in large frying-pan until hot but not brown. Brown meat on both sides; remove to platter. Add sliced onions to frying-pan and fry lightly; remove from pan. Add water to frying-pan, scraping pan to loosen any bits of beef. Return meat to pan; cover with onion slices. Add vinegar, mustard, bay leaf and cloves. Cover and cook slowly 1 1/2 hours or until tender, turning every 1/2 hour. Place steaks on serving platter. Remove bay leaf and cloves and place onions on platter. Granish each steak with 1 spiced onion and 3 pimiento strips.